1. Field of the Invention
This invention relates to a process for the production of a rubber closure or plug for a medical vial or bottle and a resin-laminated rubber closure member produced thereby.
2. Description of the Prior Art
Rubber closures for vials, containing vulcanization accelerators or other compounding agents, have hitherto been fraught with problems in that medical or pharmaceutical products held by such rubber closures are deteriorated during preparation or storage by these agents, i.e. contaminated with fine particles thereof.
In order to solve such a problem, there have been proposed rubber closures for vials, in which the leg part is wholly laminated with a fluoro resin to prevent the rubber of the leg part from direct contact with a solution of a medical or pharmaceutical product, thus preventing impurities contained in the rubber from dissolving in the solution (Japanese Patent Publication Nos. 9119/1979 and 1355/1977 and Utility Model Publication Nos. 27753/1969, 17831/1970 and 21346/1974). For the production of such a rubber closure or stopper, the inventor has also proposed a process for producing a laminated rubber closure by a two stage molding as shown in FIG. 3 (Japanese Patent Publication No. 53184/1982). That is, this process comprises a first step of placing a chemical-resistant resin film 4 with a larger size than the outer diameter of a finished product and a non-vulcanized rubber sheet 5 in this order on a lower metal mold 2 with an annular recess for forming an annular leg part of a rubber closure to be inserted into the mouth of a vial, placing an upper metal mold 1 thereon, heating and pressing them between the lower metal mold 2 and upper metal mold 1 to form a base body whose lower surface is covered with the resin film and whose upper surface is an exposed rubber surface and then cutting the flange part 7 of the base body, in contact with the rim of the vial neck, to give a width of at most 2/3 times that of the finished product, thereby forming an intermediate closure, and a second step of stacking another non-vulcanized rubber sheet 11 on the upper surface of the intermediate closure charged in the lower metal mold and heating and pressing them by the use of another upper metal mold having a recess 12 for forming an enlarged cap part with the same diameter as the outer diameter of the flange part of the finished product, in contact with the rim of the vial neck, thereby forming the finished product.
Lately, in order to improve the quality of a medical drug such as cephalosporin, it has been required to maintain the vial airtight for a longer period of time than in the prior art. The inventors have conducted studies to meet with this requirement and thus have proposed a resin-laminated rubber closure A as shown in FIG. 4 in which the outer circumference of the upper end 2 of the annular leg part is not laminated to expose the rubber surface (Japanese Utility Model Application No. 116191/1984). Production of this rubber closure can be carried out by the above described processed proposed by applicant, in which the flange part 7 of the base body is cut so as to retain no burr in the first step, but the production efficiency is very low.